1. Technical Field
This disclosure generally relates to bottles and more particularly related to bottles with improved top loading resistance.
2. Description of the Related Art
Liquid, flowable and/or squeezable consumer products have been marketed in plastic bottles, such as those made of polyolefins or polyesters. Exemplary bottle materials include polypropylene (PP) and polyethylene terephthalate (PET). While conventionally packaged in non-transparent containers with relatively thick sidewalls, larger quantities (e.g. 500-2000 mL) of heavier products, such as cleaning or detergent liquids, are now capable of being packaged in durable and recyclable plastic bottles with transparent and relatively thinner sidewalls.
Those bottles filled with liquid products often need to be vertically stacked on top of one another, such as during transportation, warehouse storage and/or at point-of-purchase display. The top loading resistance of the bottles required for stacking may depend upon the type of products and the specific stacking configurations. However, conventional plastic bottles generally have limited and insufficient top loading resistance, especially when the products are heavier liquids. As a result, bottles filled with liquid products in the bottom may be subjected to substantial top loading forces and may buckle or even collapse, causing economic loss in terms of inventory replacement and the labor needed for clean-up, or damage to the facility or vehicle in which the collapse occurs.
Accordingly, efforts have been directed to increasing the top loading resistance of plastic bottles. For example, additional structural features such as sidewall ribs, sidewall panels, and bottom ribs, have been found to improve the top loading resistance of plastic bottles. These structural features, however, are not without their cost. In particular, the panels and ribs often require more plastic material to be used, which is undesirable both economically and environmentally.
Bottles with variable wall thickness are also known in the art. For example, it has been found that gradual thickening of the sidewall (up to four times), both upwardly toward the shoulder and neck portions and downwardly toward the bottom base portion, improves bottle strength against laterally imposed stacking and crushing loads, such as in a vending machine. However, the effectiveness of such wall thickness profile against top loading forces remains to be established.